In general, a VCR includes a pair of transformers for transmitting signals read from a tape by a plurality of heads to a signal processing system therein. One of the pair of transformers is attached on a rotary drum and the other thereof is attached on a stationary drum in the VCR. In attaching the transformers to the drums, it is important to fix the transformers parallel to the drums.
As is shown in FIG. 1, a typical head drum assembly for use in a video cassette recorder includes a rotating shaft 1, a rotary drum 2, a stationary drum 4, a lower and an upper bearings 5, 5', a rotary transformer 6 and a stationary transformer 7.
The rotary drum 2 with a protruding annular portion 3 is tightly fixed to an upper portion of the rotating shaft 1 and the stationary drum 4 rotatably supports the rotating shaft 1 through the lower and the upper bearings 5, 5', wherein the upper and the lower bearings 5, 5' connect the upper and the lower parts of the stationary drum 4 to the lower portion of the rotating shaft 1, respectively.
The rotary transformer 6 may be fixedly attached at the protruding annular portion 3 of the rotary drum 2 using a bonding agent (not shown) and a rotary transformer fixing apparatus.
There is shown in FIG. 2 a cross sectional view of a conventional rotary transformer fixing apparatus 60. As shown, the apparatus 60 includes a sliding member 10, a rod 20 for guiding the movement of the sliding member 10, a holder 30, an integral part of the sliding member 10, and a pressing plate 40 attached at the bottom of the holder 30. The rotary drum 2 is placed upside-down on a jig 50 and the rotary transformer 6 is set on a terminal surface 3a of the protruding annular portion 3 thereof, wherein the terminal surface 3a is applied with the bonding agent.
After the rotary transformer 6 is set on the terminal surface 3a of the protruding annular portion 3 of the rotary drum 2, the sliding member 10 operated by a driving means (not shown) is moved vertically along the guide rod 20, resulting in moving the holder 30 vertically upward or downward. When the holder 30 is moved downward, the pressing plate 40, in turn, presses the upper surface of the rotary transformer 6 for a predetermined time, thereby fixedly attaching it to the rotary drum 2.
However, with such a rotary transformer fixing apparatus, it is difficult to properly attach the rotary transformer on the terminal surface of the protruding annular portion of the rotary drum, since the pressing plate may not apply a uniform pressure to the rotary transformer during the pressing operation thereof due to the distance between it and the sliding member. In addition, the rotary transformer may be damaged by the direct contact with the pressing plate.